Agriculture Reference
In-Depth Information
Effects of water supply on the growth and
nutrient content of fruiting trees of 'Golden Delicious'/'M.
Table
.
'
Water rate (%)
Root dry weight (kg/tree) .
.
.
Total dry weight (kg/tree)
.
.
.
N content (g/tree)
.
.
.
P content (g/tree)
.
.
.
K content (g/tree)
.
.
.
Calculated from data of Buwalda and Lenz ().
suggests that enhanced rooting in the surface zone is a contributory cause of
excess K uptake from herbicide strips.
Effects of water stress and irrigation: fertigation
Shortage of water may influence nutrient uptake in several different ways. Low
soil water potentials in the rooting volume may adversely affect the supply of
nutrients moving largely by diffusion, e.g. K and P (Marschner,
). The
effective length of root can be considered as that in soil at a water potential
greater than
MPa. The drying of unirrigated soil in England in spring
and early summer under grass management can reduce 'effective' apple root
densityfrom
−
.
cmcm
−
byearly June(Atkinson,
).Leafexpansion
is, however, usually checked by less severe levels of water stress than are other
plant processes including root growth. Plant growth is therefore checked by
low water potentials through effects on leaf area and total photosynthesis.
This is likely to reduce sink demand for nutrients by the shoots and therefore
nutrient uptake. In lysimeter experiments reduction of water supply to
.
to
.
%or
' reduced
N, P and K uptake in approximate proportion to the reduction in total growth
(Buwalda and Lenz,
% of that consumed by control trees of 'Golden Delicious'/'M.
). This was despite the fact that root growth was not
reduced at lower irrigation levels (Table
).
On some soils excessive water supply by precipitation plus irrigation can
cause very large amounts of N to be leached from the soil (Neilsen and Neilsen,
.
).
Apple root systems adjust very quickly to localization of water supply.
Trees which had been irrigated for many years by surface irrigation, and had
widespread root systems, adjusted their roots to a very small wetted volume of
soil within one season of localized drip irrigation (Levin
et al.
,
). Vegetative
growth and cropping were not reduced. The root distribution pattern of trees
irrigated by tricklers depends mainly on the wetted soil volume, which may be
